1. Field of the Invention
The present invention relates to magnetic flux control means for a permanent-magnet motor-generator that is comprised of a rotor of permanent-magnet pieces supported for rotation in a stator housing, and a stator surrounding around an outside periphery of the rotor.
2. Description of the Prior Art
Modern advanced permanent magnets of high performance have become much employed on a rotor of a motor-generator. Moreover, as the motor-generator having the rotor structure of permanent magnets is high in efficiency of electromechanical energy conversion and simple in construction, its use has recently grown in industrial machines and instruments of various kinds. Then, much research and development have continued to make the motor-generator compact or slim in construction, with even high performance and high power output, and correspondingly necessitated a growing variety of parts and components. In order to increase a torque at low speed in operation of the conventional motor-generators, it is effective to increase the strength of the magnetic field of the stator around the rotor, thereby raising the torque. With the motor-generators, thus, increasing well the torque causes the increase of electromotive force at a low speed, contributing to the provision of commercially viable power source for machines.
Among the conventional a-c motor-generators capable of developing high-power output, there is a motor-generator disclosed in Japanese Patent Laid-Open No. 236260/1995, which is co-pending application of the present inventor. The prior motor-generator controls magnetic flux density in proportion to the speed in revolutions per minute (rpm) of the rotor to adjust properly an amount of the generated amperes or voltages. To cope with this, a control ring is arranged between the rotor and the stator for rotation relatively of them and further a magnetic flux permeable member is provided in the control ring.
Further disclosed in Japanese Patent Laid-Open No. 261988/2000, which is also co-pending application of the present inventor, is a motor-generator in which a cylindrical controller member is arranged on the inside surface of the stator, the cylindrical controller member being formed of magnetic permeable pieces and non-permeable pieces, which alternate in position circularly in the form of a cylinder. The cylindrical controller member is moved selectively to any angular position relatively to the stator in accordance with an operating phase of the motor-generator. That is to say, to get it started, the cylindrical controller member is moved to an angular position where the magnetic flux permeable pieces of the controller member are brought into radial alignment with the teeth of the stator, each to each tooth. In contrast, when the rotor comes to rest, the cylindrical controller member is moved to another angular position where the magnetic flux permeable pieces may be cooperative with the teeth of the stator core to provide the magnetic path around the overall circumference of the controller member, thus allowing the magnetic flux to pass circumferentially of the controller member with a uniform distribution, thereby ensuring smooth rotation of the rotor.
In conventional motor-generators, there is a way in which the on-off switch operation of a power transistor chops the generated power to produce a chopped voltage. However, this way has a major problem of causing a high ripple voltage, which makes it tough to control the generated power. With the prior motor-generator disclosed in the senior application stated earlier, there is provided an annular member composed of magnetic flux permeable pieces arranged circularly at a pitch equal to a stator tooth pitch, with resinous pieces being each interposed between any adjoining magnetic flux permeable pieces so as to match the stator slots. The annular member is installed around the rotor for angular movement relatively to the stator. At low speed in rpm the annular member is moved to an angular position where the magnetic flux permeable pieces come in radial alignment with the stator teeth. In contrast, when the rotor is driven at a high speed, the annular member is shifted to another angular position where the magnetic flux permeable pieces are each displaced out of the alignment with the associated stator tooth to reduce an area allowing the magnetic flux to pass through there. With the construction in which the magnetic flux permeable pieces are arranged intermittently and jointed together with resinous pieces to form a cylinder, the resinous pieces are much subjected to wear during revolution of the rotor. Moreover, the annular member, since being subject to restoring force, experiences a large force rendering magnetism much more when the magnetic path is reduced. This makes a troublesome problem of causing deformation of the annular member, which might lead to breakage of the annular member.
In conventional motor-generators, there is a way in which the on-off switch operation of a power transistor chops the generated power to produce a chopped voltage. However, this way has a major problem of causing a high ripple voltage, which makes it tough to control the generated power. With the prior motor-generator disclosed in the senior application stated earlier, there is provided an annular member composed of permeable pieces arranged circularly at a pitch equal to a stator tooth pitch, with resinous pieces being each interposed between any adjoining permeable pieces so as to match the stator slots. The annular member is installed around the rotor for angular movement relatively to the stator. At low speed in rpm the annular member is moved to an angular position where the permeable pieces come in radial alignment with the stator teeth. In contrast, when the rotor is driven at a high speed, the annular member is shifted to another angular position where the permeable pieces are each displaced out of the alignment with the associated stator tooth to reduce an area allowing the magnetic flux to pass through there. With the construction in which the permeable pieces are arranged intermittently and jointed together with resinous pieces to form a cylinder, the resinous pieces are much subjected to wear during revolution of the rotor. Moreover, the annular member, since being subject to restoring force, experiences a large force rendering magnetism much more when the magnetic path is reduced. This makes a troublesome problem of causing deformation of the annular member, which might lead to breakage of the annular member.
The permanent-magnet generators need exploiting the greatest possible magnetic force inherent to the permanent magnets while reducing the magnetic force as the speed in rpm of the rotor increases. To cope with this, it is conceivable to provide a generator in which more than one winding is wound in phase on the stator core in a manner to increase the voltage as the rpm rises. According to the generator constructed as stated just above, the production of a desired constant voltage will be realized easily by a way of controlling the magnetic flux passing through the stator in light of an electric current induced in the windings.
The output (U) of the permanent-magnet motor-generator is determined, depending on the magnitude of magnetic force of the permanent magnet, the number of loops or turns of the stator windings and the speed in rpm of the rotor, and is given mathematically by
U=31/2xc2x7(2xcfx80f/21/2)xc2x7xcfx86w1xc2x7kw1
where f is the frequency, xcfx86 is the magnetic flux density, w1 the number of turns and kw1 a factor. Here the magnetic flux density is determined in terms of the relation between the magnetic force and magnetic resistance of the permanent magnet, and written in
xcfx86=Ni/Rm, where Ni is the magnetomotive force and Rm is the magnetic resistance.
The magnetic resistance is equal to the magnetomotive force divided by the magnetic flux, or
Rm=L1/(xcexcxc2x7S1), where L1 is a distance, S1 is an area and xcexc is any relative permeability of any material determined on the basis of the permeability of air.
Moreover, the permanent-magnet motor-generators may produce the high output. Since they do not, however, contain any means for controlling the magnetic flux when the rotor is driven at high rpm, they are difficult of control of the generated power. With the motor-generator serving as a motor, especially, an electrical potential has to be applied against the generated high voltage, otherwise it is quite hard to produce any high voltage.
A prior approach to the resolution of the problem as stated just above is the permanent-magnet generator disclosed in Japanese Patent Laid-Open No. 261988/2000 recited earlier. With the prior generator, since the magnetic flux permeable pieces are arranged intermittently and jointed together with resinous pieces to form the annular member, the resinous pieces are much subjected to wear during revolution of the rotor. Moreover, the annular member, since being subject to restoring force, experiences a large force rendering magnetism much more when the magnetic path is reduced. This makes a troublesome problem of causing deformation of the annular member, which might lead to breakage of the annular member.
Another problem faced in the motor-generator resides in the magnetic path, more particular, the air gap between the rotor and the stator. The permeability of air is 4xcfx80xc3x9710xe2x88x927(Hxe2x96xa1m), whereas the permeability of silicon steel containing 3% Si is thirty thousand times that of air and the permeability of PC nickel-iron alloys is fifty thousand times that of air. That is, both the alloys have extraordinary high magnetic permeability as compared with air. It will be thus appreciated that any cylindrical member for controlling magnetic flux, arranged around the outside periphery of the rotor for angular movement relatively to the stator with keeping either close contact with or any infinitesimal clearance spaced apart from the tooth tips of stator teeth, may help ensure a magnetic path well in efficiency of the motor-generator. Nevertheless, the cylindrical member recited just above, as constructed in a structure that magnetic flux permeable pieces and nonmagnetic pieces alternate circularly with each other, has a disadvantage that the magnetic flux density is too restricted at an area where any magnetic flux permeable piece intersects any nonmagnetic piece, thereby rendering the magnetic field entering the stator too small.
Even if it were allowed, in light to air less in permeability, to form the stator itself in a construction making it possible to restrict the flow of flux passing through the stator core, the magnetic flux density passing through the stator would be well controlled with no provision of the conventional magnetic-flux control means such as the cylindrical member for control of the magnetic flux, which is composed of the magnetic flux permeable pieces combined with the nonmagnetic pieces and arranged between the stator and the rotor revolving at high speed in rpm. This concept to form the stator itself in a construction making it possible to restrict the flux passing through the stator core posses no problem of encountering wear of the magnetic flux permeable and nonmagnetic pieces in the cylindrical member for control of the magnetic flux and also occurrence of accidental collision of the cylindrical member with the revolving rotor. Moreover, there is no fear of cracking and/or breakage at an interface between any adjacent magnetic flux permeable and nonmagnetic pieces, which might occur due to difference in linear expansion coefficient, hardness and so on between materials of the magnetic flux permeable and nonmagnetic pieces.
After having evaluated the design considerations of the permanent-magnet motor-generator on the basis of the equations recited earlier, it has become evident that the magnetic flux is dominantly controlled by the influence of the air gap on the magnitude of magnetic force because air is extremely large in magnetic resistance. For example, with the motor-generator of 60 mm long having a rotor of about 60 mm in diameter with an air gap of about 1.5 mm being provided between the confronting stator and rotor, the magnetic resistance of the air gap is 3.33xc3x97106 while the magnetic resistance of the rotor is 2.1xc3x97103. Thus, it will be understood that the air is fifteen hundred times larger in magnetic resistance than the rotor. No simple means for controlling the magnetic flux density has been devised heretofore for the motor-generator having the characteristics recited above.
However, even the motor-generator having the magnetic flux permeable member made extremely small in area contains still a drawback to be resolved, in which it does not control positively the inferior permeability, or nonmagnetic property of air. Moreover, as opposed to the motor-generator of the type having the generation characteristics in which the voltage rises in proportion to the increase of rpm, the motor-generator of the type stated earlier will be reduced in the rate of voltage rise. Nevertheless, the decrease in the rate of voltage rise is too slow to always meet the desired characteristics.
It is a primary object of the present invention to overcome the problems stated earlier and to provide magnetic flux control means for a motor-generator, in which switching means change over connections among high-tension windings, low-tension windings and variable-voltage windings to produce any desired voltage, and an annular member installed between a stator and a rotor is angularly moved in such a manner that a strength of magnetic flux decreases to depress occurrence of a reaction force as a speed in rpm rises, while the strength of magnetic flux at a low speed in rpm is realized by a magnetic force intrinsic to a permanent magnet, thereby helping ensure generating always a desired constant voltage independently of any variation in rpm of the rotor.
With the magnetic flux control means according to the present, moreover, there is provided an annular member of a simple construction in which magnetic permeable pieces and nonmagnetic pieces are arranged alternately to form a cylinder and joined together to ensure steady mechanical strength of the annular member, the magnetic flux permeable pieces being chamfered at corners on a radially outside circumference of the annular member. The annular member may be moved angularly in a steady sliding manner in response to the variation in rpm to control properly the magnetic flux, thereby ensuring always the desired constant voltage.
As an alternative, there is provided the magnetic flux control means in which a stator core is made slim in radial thickness of an outside circumferential magnetic path and a cylindrical member fits over the outside circumferential magnetic path for angular movement relative to the stator core, the cylindrical member being provided on an inside surface thereof with a series of axial grooves in which air exists instead of nonmagnetic material. Sliding rotation of the cylindrical member around the stator core results in controlling the magnetic flux.
Besides, the magnetic flux control means in which the magnetic permeable pieces and nonmagnetic pieces alternate circularly to form a cylinder is designed so as to keep the annular member against uneven wear, preventing the outside surface of the annular member from interfering with the tooth tips inside the stator core, thus ensuring the secure sliding rotation of the annular member to control the magnetic flux.
The present invention is concerned with a magnetic flux control means for a permanent-magnet motor-generator, comprising a rotor supported for rotation in a stator housing and composed of more than one permanent-magnet piece arranged circumferentially in a way spaced apart from each other, a stator fixed to the stator housing to surround around an outside periphery of the rotor and composed of a stator core with teeth providing sequential slots, and windings laid in the slots, an annular member arranged in close contact with the stator for angular movement with keeping sliding contact with the stator, a driving means to move the annular member with respect to the stator, and a controller for energizing the driving means in response to rpm of the rotor to control a position of the annular member relatively to the stator, thereby regulating a magnetic flux density in the teeth of the stator to give a preselected desired voltage.
In an aspect of the present invention, a magnetic flux control means for a motor-generator is disclosed, in which the annular member is arranged inside the stator and comprised of a magnetic flux permeable piece less in width than the slot defined between any two adjacent teeth in the stator core, and a nonmagnetic piece interposed between any two adjacent magnetic flux permeable pieces, and in which the windings laid in the stator are composed of a high-tension winding of more than one winding set for a power source, a low-tension winding of more than one winding set and a voltage-variable winding of at least one winding set for voltage control while the controller serves for controlling on-off operation of a switching means to change over connections among the winding sets, thereby varying a number of turns of the high-tension winding and the low-tension winding.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the controller operates the switching means depending on the rpm of the rotor to either connect in any of series and parallel or leave unconnected the high-tension winding and the low-tension winding, thereby giving any desired constant voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the controller energizes the driving means to move circumferentially the annular member between an angular position where any clearance between any magnetic flux permeable piece in the annular member and the opposing tooth in the stator is made reduced so that the magnetic flux is unrestricted and another angular position where the clearance is made large so as to restrict the magnetic flux to thereby lower an output voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the controller at low speed of the rotor energizes the switching means to connect in series the windings sets of the high-tension winding, thereby increasing the number of turns of the high-tension winding, whereas at high speed of the rotor gets the switching means to leave unconnected the winding sets of the high-tension winding from each other, and further when the rpm of the rotor starts to go too higher, the controller operates the driving means to move circumferentially the annular member, whereby the high-tension winding produces a preselected desired constant voltage.
In a further aspect of the present invention a magnetic flux control means is disclosed, in which the controller at low speed of the rotor energizes the switching means to connect in series the windings sets of the low-tension winding, whereas at high speed of the rotor gets the switching means to connect the winding sets of the low-tension winding in a way to reduce the number of turns, and further when the rpm of the rotor starts to go too higher, the controller operates the switching means to either connect in parallel or leave unconnected the winding sets and also energize the driving means to move circumferentially the annular member, whereby the low-tension winding produces a preselected desired constant direct-voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the controller carries out connection control of the winding sets of the low-tension winding in a way corresponding to a signal for connection control of the winding sets of the high-tension winding.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which a voltage created in the voltage-variable winding is rectified to a variable direct voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the annular member is comprised of magnetic flux permeable pieces each of which is formed in a rectangular shape in cross section having a width less than that of the slot between any two adjacent teeth in the stator, the magnetic flux permeable pieces being arranged in juxtaposition along an inside periphery of the stator with nonmagnetic pieces being each interposed between any two magnetic flux permeable pieces, and the permeable pieces are each chamfered off at corners on a radially outside circumference of the rectangular shape in cross section to provide first chamfered areas, so that when any magnetic flux permeable piece is placed in opposition to any slot in the stator, first clearances of preselected amount are left between the first chamfered areas and widthwise opposing corners of the associated teeth on a radially inside circumference of the stator.
In a further another aspect of the present invention, a magnetic flux control means is disclosed, in which the tooth in the stator is chamfered off at its tooth tip corners to provide second chamfers so that the first clearances are formed in magnetic path clearances defined between the first and second chamfered areas.
In a further another aspect of the present invention, a magnetic flux control means is disclosed, in which a second clearance of preselected amount is provided between the inside periphery of the annular member and an outside periphery of the rotor.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the windings are wound on the teeth of the stator core in the stator so as to generate electricity in phase, and grouped into more than one winding set to be connected in series to vary a number of turns, while the controller serves for regulating angular position of the annular member with respect to the stator and further for connecting in series and/or in parallel the winding sets, depending on the rpm of the rotor, thereby giving a preselected desired voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the annular member is arranged around an outside periphery of the stator and has magnetic flux control grooves cut into an inner peripheral surface thereof, with remaining ribs between the grooves, which are extended axially of the stator and spaced apart away from each other at regular intervals around the curved inner surface, so that the sequential ribs between the slots form at their inside tips a curved surface that comes into close sliding contact with the outside periphery of the stator. Moreover, the grooves inside the annular member are each made roughly equivalent in a circumferential length with any one tooth in the stator. An outside peripheral path for magnetic flux in the stator core is made less in width by a width of a magnetic path in the annular member.
In another aspect of the invention, a magnetic flux control means is disclosed, in which the magnetic flux passing through any tooth in the stator core is restricted when any groove in the annular member comes into radial alignment with the tooth, whereas the magnetic flux passing through any tooth in the stator core remains unrestricted when any rib in the annular member comes into radial alignment with the tooth.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the grooves in the annular member are charged with nonmagnetic solid lubricant to reduce a frictional resistance that is encountered when the annular member slides over the stator core.
In a further another aspect of the present invention, a magnetic flux control means is disclosed, in which the slots in the stator are charged with resinous strengthening material to improve stiffness of the stator.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the annular member is composed of a pair of annular halves, which are arranged so as to move circumferentially in directions opposite to each other by the action of the driving means.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the driving means is a reversible motor that has a reversible rotary shaft around which a clockwise thread and a counterclockwise thread are formed, while on the annular halves there are fixed nuts that have threads, each to each nut, mating the threads around the rotary shaft, respectively.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the windings are grouped into more than one winding set, which are different from each other in a number of turns wound on the teeth of the stator core in the stator, while the controller in response to the rpm of the rotor serves to control an angular position of the annular member with respect to the stator and further to make at least any one of series and parallel connections of the winding sets, thereby giving a preselected desirable voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the controller, when the motor-generator operates as generator, connects the winding sets in series in response to a low rpm of the rotor to produce a high voltage, while connects any winding sets in parallel in response to a high rpm of the rotor to produce a large current with even desired voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the controller, when the motor-generator operates as motor, connects the winding sets in series in response to a low rpm of the rotor to produce a high magnetic force, while connects any winding sets in parallel in response to a high rpm of the rotor to reduce the number of turns to provide a desired magnetic force.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which with the windings shunt-wound in the stator core, conductors of the windings so wound as to become identical in phase are connected in series at a low rpm range and are led out on the way to reduce the number of turns as the rpm of the rotor increases, while the circumferentially shunt-wound windings are either connected in parallel or left unconnected with each other at a high rpm of the rotor to thereby allow, with being coupled with the angular position control of the annular member, to give either a constant voltage or a constant torque.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the windings on the stator are constituted in phase in matching with a number of poles of permanent magnets on the rotor, while the winding sets are connected in parallel, thereby providing the generator capable of producing a large current with even the desired voltage.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the annular member is arranged inside the stator and is comprised of density-rich magnetic flux permeable parts in which magnetic flux permeable materials are closely laminated in the form of a circle, and density-lean magnetic flux permeable parts in which magnetic flux permeable chips are arranged circularly in a manner spaced apart from each other at an interval of circumferential length equivalent to a circumferential width of the tooth and nonmagnetic chips are each arranged in a space left open between any two adjacent magnetic flux permeable chips, the nonmagnetic chips being made of nonmagnetic reinforcing material such as aluminum and so on, and the density-rich and density-lean magnetic flux permeable parts unlike in density being arranged alternately along the axial direction.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the magnetic flux permeable chips are arranged circularly in such a way to leave a space open between any two adjacent magnetic flux permeable chips, the space being equal in number to the teeth and provided at an interval of length equivalent to a circumferential width of the tooth in the stator. Moreover, both the density-rich magnetic flux permeable parts and the magnetic flux permeable chips are made of circular magnetic flux permeable plates laminated densely at an equal interval.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the density-lean parts of the annular member are each composed of annular magnetic flux permeable steel plates overlaid axially one on the other, the annular magnetic flux permeable steel plate being made of arched density-lean chips and density-rich chips, which are arranged in the form of cylinder in a manner spaced apart at an equal interval, and windows left open between chips unlike in density are filled with the nonmagnetic reinforcing material.
In a further another aspect of the present invention, a magnetic flux control means is disclosed, in which the density-rich parts of the annular member are each made of an axial lamination of a magnetic flux permeable ring and a silicon-steel plate, which are jointed together.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which an annular member of thin silicon steel plate is press-fit inside an inner surface of the teeth in the stator.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the annular member is provided at axially opposing ends thereof with outer rings, each to each end, to keep the magnetic force against leaking out from the axially opposing ends, the outer rings being made of a silicon steel plate superior in permeability.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the annular member is arranged inside the stator, with an outside periphery thereof being kept in close contact with an inner tips of the teeth in the stator for sliding movement, and the driving means includes any axial end of the annular member, to which is applied a rotating force for moving circumferentially the annular member, a rod transmitting the rotating force to the axial end, and an actuator to move in and out the rod.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the windings are wound on the teeth of the stator core in the stator so as to generate electricity in phase, and grouped into more than one winding set to be connected in series to vary a number of turns, while the controller serves for regulating angular position of the annular member with respect to the stator and further for making series and/or parallel connections among the winding sets, depending on the rpm of the rotor, thereby giving a preselected desired voltage.
In a further aspect of the present invention, a magnetic flux control means is disclosed, in which the nonmagnetic piece is either replaced with air or made of any reinforcing member of aluminum, resinous material and so on. Moreover, the annular member is made of an axial lamination of more than one ring member in which the magnetic flux permeable piece and the nonmagnetic piece are overlaid one on the other.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the driving means is composed of any axial end of the annular member, to which is applied a rotating force for moving circumferentially the annular member, a rod transmitting the rotating force to the axial end, and an actuator to move in and out the rod. As an alternative, the driving means includes a d-c motor and the controller selects more than one position of the rod sensed by a position sensor and energizes the driving means to move in and out the rod. Moreover, the driving means includes a solenoid-operated valve having a rod connected to any one axial end of the annular member, while the controller selects more than one position of the rod sensed by a position sensor and transforms a load voltage applied to the solenoid operated valve, moving the rod to rotate the annular member.
In another aspect of the present invention, a magnetic flux control means is disclosed, in which the controller has an inverter function that rectifies an electric current produced at a preselected desired voltage to output an alternating-voltage of a preselected constant voltage.
According to the magnetic flux control means constructed as stated earlier, the actuator moves the annular member to any angular position where the most desirable clearance for magnetic path may be provided between the annular member and the teeth in the stator core. This allows adequate voltage control and producing any preselected constant voltage. In addition, the magnetic flux control means governs the on-off operation of the switching means to change over the connections among the high-tension windings, low-tension windings and the variable-voltage windings, thus giving the desired voltage.
As stated above, the magnetic flux control means of the present invention, making no attempt to use the conventional electric controls, relies instead on an unique combination of the angular position control of the annular member moved by the actuator and the connection control in the high-tension windings or low-tension windings by on-off operation of the switching means. This, as occurring no output loss, heating from any electronic elements and radio trouble due to high-frequency high-voltage, allows effective control of the magnetic flux, thus helping ensure the proper voltage control, for example making it possible to produce any preselected desirable constant-voltage such as 100Vxcx9c200V, 12Vxcx9c27V and so on with less subject to the influence of variation in rpm of the rotor.
In the motor-generator of the present invention, the nonmagnetic pieces of aluminum or aluminum alloys charged by casting or the like between any two adjacent magnetic flux permeable pieces contribute to the improvement of stiffness in the annular member, which controls effectively the magnetic flux, depending on the revolving conditions of the rotor. Thus, the annular member may resist well against the reaction with the result of the improvement in durability. Accordingly, the present magnetic flux control means for the motor-generator will be suitable for use in, for example high-speed generators and motors for the conversion of mechanical energy into electrical energy or, conversely, electrical energy into mechanical energy, power supply sources for energizing refrigerators or coolers mounted on vehicles, electric power sources to energize a heater in the diesel particulate filters, generators combined in cogeneration system, electric rotating machinery coupled with the automotive engine in a hybrid vehicle, and high-speed motors operating machines such as machine tools. It is to be noted that the motor-generator with the magnetic flux control means of the present invention tolerates well the high speed of, for example 60,000 rpm, and is made slim in construction with even less production costs.
With the magnetic flux control means constructed as stated earlier, the magnetic flux permeable pieces in the annular member is made smaller in circumferential width than the slot defined between any two adjacent teeth in the stator, while chamfered off at the surface opposing the teeth tips in the stator. The construct results in providing the clearance for magnetic path between the annular member and the stator teeth, which is most suitable for proper voltage control.
In case where the motor-generator on board the vehicle is needed to serve as a electric power source of, for example 100V for power applications, the developed electric power has been conventionally subjected to phase control, then chopped in current through electric elements such as any transistor, thyristor and so on, and further the chopped voltage has been regulated with being plagued with a high-frequency power caused by the chopper circuit, then followed by rectification to be converted into an alternating current of 100V through an inverter. As opposed to the conventional way stated just above, the magnetic flux control means of the present invention has no need of phase control and, therefore does not require the electric elements as stated earlier.
Besides, since the conventional motor creates a counter emf as the rpm of the rotor increases, it takes a driving electric power of high tension enough to overcome the counter emf. In contrast, the motor-generator with the magnetic flux control means of the present invention, as allowing to suppress the development of the counter emf, succeeds in much reducing the driving electric power.
In the magnetic flux control means of the present invention, moreover, there is provided the annular member containing a skeletal structure of magnetic flux permeable pieces chamfered at their circumferentially opposing corners on the radially-outside curved surface, and nonmagnetic pieces of aluminum and so on less in relative permeability poured by casting in the spaces between any adjacent magnetic flux permeable pieces to surround around each the magnetic flux permeable pieces, including their chamfered tips. Thus, the magnetic flux control means of the present invention is not only improved in electromagnetic property, but also made steady in mechanical stiffness so as to be able to stand up certainly the reaction.
When the rpm of the rotor starts to go too higher, the annular member high in stiffness is moved circumferentially to any angular position where any magnetic flux permeable piece is offset circumferentially out of the radial alignment with the associated tooth in the stator, so that the magnetic flux passing through the teeth will be restricted to make the produced power less in voltage. To cope with such event that a simple movement of the annular member is insufficient to restrict the magnetic flux to the extent where the developed power at high speed in rpm of the rotor may be lowered to a desirable voltage, the windings laid in the slots in the stator are made to be varied in a number of turns. That is to say, the windings are grouped into more than one winding set that may be changed in connection among them. Thus, the winding sets at low speed in rpm of the rotor are connected in series to increase the number of turns, whereas at high speed connected in parallel or left alone to reduce the number of turns. This allows regulating the developed power to give a preselected desirable voltage, thus makes it possible to easily produce a constant d-c voltage of, for example 100V for automotive auxiliaries, especially would make easy to give a constant voltage in the three-phase generators.
In the magnetic flux control means of the present invention, there is provided an annular member that density-rich magnetic flux permeable pieces are arranged circularly in a continual manner so that the part subjected to wear continues around the overall periphery. This arrangement allows reducing uneven wear to the minimum, thereby not only making the steady sliding revolution possible but also realizing strength retention of the annular member itself. According to the magnetic flux control means having the annular member in which the magnetic flux permeable pieces are chamfered at their widthwise opposing corners, the clearance defined between the annular member and any tooth in the stator may be reduced to an extent of 0.05xcx9c0.1 mm, while the clearance between the annular member and the rotor will be reduced to an extent of 0.5xcx9c0.1 mm, so that the loss in magnetic path may be much reduced. Moreover, this allows keeping the clearance between the annular member and the rotor minimum and correspondingly raising efficiency.
As an alternative, there is provided a magnetic flux control means in which the annular member is arranged around an outside periphery of the stator and has magnetic flux control grooves cut into an inner peripheral surface thereof, with remaining ribs between the grooves. With the annular member modified as stated earlier, the magnetic flux will have nowhere to pass when the ribs in the annular member are displaced out of the teeth in the stator, so that the magnetic flux is restricted. Nevertheless, the modified annular member is apt to experiences uneven movement due to a reaction that is caused by bending the magnetic path when the magnetic flux is restricted. To cope with this, the annular member is divided axially into two halves, which are allowed to move circumferentially in directions opposite to each other to thereby counteract the reaction, thus helping ensure the smooth angular movement of the annular member. Moreover, the modified annular member, as made of monolithic material high in strength and permeability, is free of any problem in mechanical strength. Accordingly, the modified annular member is made steady in mechanical strength and also less subject to uneven wear, which might otherwise occur in the ribs in the annular member sliding over the stator, thus, ensuring the steady sliding movement along the stator.
When the rpm of the rotor starts to go too higher, the annular member high in stiffness slides circumferentially to any angular position where any rib is shift circumferentially out of the associated tooth in the stator core, instead any groove is placed in radial alignment with the tooth, so that the magnetic flux passing through the teeth will be restricted to make the produced power less in voltage. To cope with such event that a simple movement of the annular member is insufficient to restrict the magnetic flux to the extent where the developed power at high speed in rpm of the rotor may be lowered to a desirable voltage, the windings laid in the slots in the stator are grouped into more than one winding set that may be changed in connection among them to vary the number of turns in the windings. Thus, the winding sets at low speed in rpm of the rotor are connected in series to increase the number of turns, whereas at high speed connected in parallel or left alone to reduce the number of turns. This allows regulating the developed power to give a preselected desirable voltage, thus makes it possible to easily produce a constant d-c voltage of, for example 100V for energizing various auxiliaries onboard vehicle.
In the magnetic flux control means constructed as described above, the annular member may be kept minimum in uneven wear so as to ensure the certain strength of the annular member itself. In contrast, although the stator cooperating with the annular member in the magnetic flux means is made discontinuous between any tooth and the adjacent slot, an occurrence of interference and so on will be eliminated by circumferential close contact of the annular member with the outside peripheral path for magnetic flux of the stator core. According to the magnetic flux control means having the modified annular member constructed as stated earlier, moreover the clearance across between the annular member and any tooth in the stator may be reduced to an extent of 0.05xcx9c0.1 mm, so that the loss in magnetic path may be much reduced. Moreover, this also allows keeping the clearance between the teeth in the stator core and the rotor minimum and correspondingly raising efficiency.
As a further alternative, there is provided a magnetic flux control means having the annular member, which is comprised of density-rich magnetic flux permeable parts in which magnetic flux permeable materials are closely laminated in the form of a circle, and density-lean magnetic flux permeable parts in which magnetic flux permeable chips are arranged circularly in a manner spaced apart from each other at an interval of circumferential length equivalent to a circumferential width of the tooth and nonmagnetic chips are each arranged in a space left open between any two adjacent magnetic flux permeable chips, the nonmagnetic chips being made of nonmagnetic reinforcing material such as aluminum and so on, and the density-rich and density-lean magnetic flux permeable parts unlike in density being arranged alternately along the axial direction. With the magnetic flux control means constructed as state just above, the magnetic flux will have nowhere to pass in an event where any magnetic flux permeable chip is placed out of the teeth in the stator, so that the rotor should not be able to revolve with smoothness. But the presence of the density-rich parts, although restricting the magnetic flux, helps ensure the smooth rotation of the rotor. Moreover, the annular member is apt to experiences a reaction that is caused by bending the magnetic path when the magnetic flux is restricted. To cope with this, the nonmagnetic chips are made of reinforcing materials such as aluminum and so on, instead of resinous material, thus resisting well against the reaction. The density-rich part in the annular member, since made of a circular continuity, not only contributes to increasing strength of the annular member, but also makes the surface sliding over the stator smooth, thereby keeping the uneven wear minimum. This helps always ensure the steady angular movement of the annular member. In other words, the stator is made circumferentially discontinuous between the slots and the teeth alternating circularly, whereas the annular member has some continuities of density-rich magnetic flux permeable part, arranged axially in a manner spaced apart from each other at an axial interval. This allows the annular member to move circumferentially with smoothness.
When the rpm of the rotor starts to go too higher, the annular member high in stiffness slides circumferentially to any angular position where any permeable chip is offset circumferentially out of the associated tooth in the stator, so that the magnetic flux passing through the teeth will be restricted to make the produced power less in voltage. Moreover, to cope with such condition that a simple movement of the annular member is still insufficient to restrict the magnetic flux to the extent where the developed power at high speed in rpm of the rotor may be lowered to a desirable voltage, the windings laid in the slots in the stator are made to be varied in a number of turns. That is to say, the windings are grouped into more than one winding set that may be changed in connection among them. Thus, the winding sets at low speed in rpm of the rotor are connected in series to increase the number of turns, whereas at high speed connected in parallel or left unconnected alone to reduce the number of turns. This allows regulating the developed power to give a preselected desirable voltage, thus makes it possible to easily produce a constant voltage of, for example 100V for various auxiliaries onboard vehicle.
The density-rich part in the annular member, since formed as a circular continuity, has the continuous surface allowed sliding circumferentially over the stator with smoothness, thereby keeping the uneven wear minimum. This helps always ensure not only the steady angular movement of the annular member, but also the secure strength of the annular member itself. In the magnetic flux control means constructed as stated above, although the stator is made discontinuous between any tooth and the adjacent slot, an occurrence of interference and so on will be eliminated by circumferentially close contact of the density-rich parts in the annular member with the stator core.
In the meantime when two solid surfaces slide or tend to slide over each other, the smoother the rubbing surfaces are made, the easier the surfaces are allowed sliding one another. The magnetic flux control means of the present invention has a construction well suited for operating on the physical principle stated just above. A hollow cylinder of thin silicon steel sheet is press-fit inside the inner periphery of the teeth in the stator to make the inner surface of the stator even to provide a smooth angular movement of the annular member. Typically, the rotor, as long in axial direction, is apt to be bent and, therefore sometimes subject to pole interference at any unbalanced area. With the permanent-magnet motor-generators, the problem stated earlier becomes critical because the air gap should be made less to establish the greater magnetic force. In contrast, the air gap increased in clearance to keep the rotor against the contact with the annular member disadvantageously results in much loss in magnetic force. In the permanent-magnet motor-generator, there is provided a construction in which the hollow cylinder is press-fit inside the teeth in the stator to help reduce the clearance between the annular member and the teeth in the stator.
If considering the stiffness of the annular member, the annular member, since small in inside diameter with even, is lacking in stiffness. The annular member, when experiencing at any axial end thereof a torque trending to rotate it, will make an attempt to return against a force bending the magnetic force. Thus, the annular member as a whole experiences a large twisting motion. To cope with this twisting motion, the annular member of the present invention has embedded with strengthening material such as aluminum and so on to have the stiffness enough to stand up against the twisting motion. Moreover, the magnetic force of the permanent magnet is very great and therefore the flux density in the magnetic path exhibits about 0.4 tesla even if cast iron is used. This means that when the magnetic path is restricted at axially opposing ends of the rotor, the magnetic force will leak out outside the motor-generator. To cope with this, it will be preferred to arrange discs of any material superior in permeability on the axially opposing ends of the annular member, each to each end.
Other objects and features of the present invention will be more apparent to those skilled in the art on consideration of the accompanying drawings and following specification wherein are disclosed preferred embodiments of the present invention with understanding that such variations, modifications and elimination of parts may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.